This invention relates generally to injection molding and more particularly to valve gated apparatus having a locating insert mounted at the front end of each nozzle having an inwardly extending spiral blade or blades to accurately locate the reciprocating valve member in alignment with the gate.
Valve gated injection molding with actuating mechanism connected to the rear end of the valve member is well known. Often the valve member is located in alignment with the gate by the bore where it passes through the manifold and a sealing bushing near its rear end. An example of this is shown in U.S. Pat. No. 5,022,846 to Schmidt which issued Jun. 11, 1991. However, this has the disadvantage that the location of the reciprocating valve member is not always maintained sufficiently accurately, particularly if the gate is cylindrical.
It is also known to provide three inwardly extending locating pins or fins to guide the valve member near its front end. An example of this is shown at page 43 of D-M-E brochure OVG2 entitled "D-M-E/OSCO Valve Gate Runnerless Molding Systems". While this improves location of the valve member, the pins or straight fins have the disadvantage that flow lines can be produced in the product by the melt parting to flow past the locating pins or fins.
A nozzle tip having spiral channels extending around the valve member to impart a swirling motion to the melt entering the cavity is also known. This is seen in the applicants' U.S. Pat. No. 4,303,382 which issued Dec. 1, 1981.